Encountered X Read Failures!

 We are still in a world that means that a premier enterprise backup agent needs kernel modules compiled for current Debian / Ubuntu releases. We are not talking about bleeding edge kernel 4.x.x here we are talking about 3.19.x (3.19.8 considered currently EOL stable, 4.0.5 considered stable, and 4.1 in RC).
Here we have to agent side log extracts – which saw a lot of lines, and then a phenominally high number of errors and what is essentially a “no” on the backup working front.
...
[2015-Jun-09 08:17:14],[ INFO],[10.10.10.1:56514],
  Retrying IO for block 1189040 of length 65536 for error 
  'Input/output error' try #2 
[2015-Jun-09 08:17:14],[ INFO],[10.10.10.1:6514],
  Retrying IO for block 1189056 of length 65536 for error 
  'Input/output error' try #2 
[2015-Jun-09 08:49:27],[ERROR],10.10.10.1:56514],
  Encountered 5972430 read failures! 

...
[2015-Jun-08 14:29:51],[ INFO],[10.10.10.1:59985],
  Retrying IO for block 21011184 of length 65536 for error
  'Input/output error' try #2 
[2015-Jun-08 14:29:51],[ INFO],[10.10.10.1:59985],
  Retrying IO for block 21011200 of length 65536 for error 
  'Input/output error' try #2 
[2015-Jun-08 14:39:00],[ERROR],[10.10.10.1:59985],
  Encountered 2075172 read failures! 

These are two separate hosts, one has a SAS RAID controller with SAS drives, one is a software RAID using mdadm and two SATA drives. These are not similar configurations, both EXT4 file systems – carrying out very different tasks. They are running the same operating system, at the same patch level. All failing to backup. Odd huh? So … I assumed it was me.
Just out of curiosity – I thought I would raise a ticket as this was – I am sure – just a coincidence I was seeing across the platforms running this kernel and backup agent.
This is the response I got.
…This is a known issue at this time. …” — Technical Support
Really? REALLY? A module I had to provide them with build libraries for the stock standard and current kernel for that distribution  that they then provided me with –  a week of struggling to get it to work and some curious host lock ups along the way…. it’s a good job this isn’t a premium pay for product!

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